Various polymers, swellable clays, and articles of manufacture have been applied to the surface of soil to provide a waterproofing layer to prevent the penetration of water and hazardous or toxic materials into the earth, and to provide lagoons, ponds and other water containment areas. Water-swellable clays, such as bentonite, have been applied directly to the soil surface and impacted in place, as disclosed in this assignee's prior U.S. Pat. No. 3,986,365. In addition, many different multi-layered articles of manufacture containing a water-swellable clay, such as bentonite, have been manufactured by adhesively securing the water-swellable clay to major interior surfaces of flexible sheet materials for application to the soil surface in abutting or overlapping relation of adjoining multi-layered articles. Examples of flexible sheet materials containing adhesively secured water-swellable clays are found in the following U.S. patents: Clem U.S. Pat. No. 4,467,015; Clem U.S. Pat. No. 4,501,788; McGroarty et al U.S. Pat. No. 4,693,923; Harriett U.S. Pat. No. 4,656,062; and Harriett U.S. Pat. No. 4,787,780.
U.K. published patent application GB 2,202,185A discloses a layer of water-swellable bentonite between flexible layers that have been needle punched together in a needle loom that secures material from a lower layer of non-woven textile material to an upper layer of non-woven textile material, and secures material from an upper non-woven textile material to the lower non-woven textile material.
Another waterproofing barrier, disclosed in Blias U.S. Pat. No. 4,344,722, is constructed in the field by applying a first flexible, water-permeable fabric layer, overlaying a thickness of water-swellable clay material and applying an overlayer of the same flexible, water-permeable fabric thereover. Other patents disclosing the use of water-impermeable layers for protecting a soil surface include British Patent Specification 1,059,363; British Patent Specification 1,029,513 and British Patent Specification 1,129,840.
While the Blias waterproofing barrier does not require the use of adhesive because the multiple layers are assembled at their final location, this at-site assembly is disadvantageous because of the increased man hours necessary to construct the barrier at the site and because of the attendant difficulty in applying a uniform thickness of the water-swellable clay over the lower fabric layer with relatively crude construction equipment.
The above disadvantages of adhesively affixing the water-swellable clay to upper and lower fabric layers over their full internal, major surface areas or assembling a multi-layer article at the site of application are overcome in accordance with the principles of the present invention, as will be described in more detail hereinafter.
It has been found that needle looming limits the types of fabrics such that at least one of the fabric layers must be a non-woven material. Needle looming also results in relatively large apertures in the fabrics so that too much of the bentonite is lost from the product during handling. Further, heavy nonwoven fabrics, together with relatively large needle punch densities results in a great number of fibrous interconnections between top and bottom fabric layers that act as water channels that channel water from one fabric layer to the other, thereby permitting the water to pass through the waterproofing membrane, by a fabric wicking action, by-passing the water-swellable clay layer.